Beomaster 8000: Step Five - Rebuilding the Displays and Indicator Lights with SMD LEDs

No Beomaster 8000 restoration is complete without rebuilding the displays. They will all fail eventually, and most in the near future. And since those beautiful large LED displays are a main design feature of this lovely receiver, nothing is more frustrating than having a few missing segments. No matter how good the condition of the enclosure, when the displays are not complete it just looks sad! Not beolovely at all!

Luckily the displays are large enough that one can update them with 0603 packaged SMD LEDs, which can still soldered fairly well by hand. For this to happen one needs to extract the displays from the display board:

Once liberated, the next step is to open them up and scrape off the original LEDs, which are directly bonded to the PCB...truly a 1980s design!:

Once the pads are prepared it is time to line up the SMD LEDs and solder them into the places of the original LEDs:

The critical element here is to place the SMD LEDs precisely into the areas that are underneath the light guides in the LED assemblies (white parts with long slots in the picture above) when assembled. If they are not centered, the LEDs will get damaged during re-assembling the displays since the light guides will exert lateral pressure on the LED packages, which can result in them breaking off their pads. I do this by soldering the LEDs on only one side, then checking where the LEDs come close to the light guide slot walls, and then I correct the position of those that are a bit off. Once all are properly in place, I solder them on the other side.

After soldering all the LEDs in, it was time to give the boards their first 24 hrs test. For this I have a breadboard setup that mimics the wiring on the display PCB:

Let's see if they are still all on tomorrow!

Beomaster 8000: Step Four - Rebuilding the FM Tuner, Preamplifier and Control Panel PCBs

After completing the power supply restoration of the Beomaster 8000 that I am rebuilding right now, it was time to do the remaining boards. While it is relatively rare to find a dead capacitor on the FM tuner, preamplifier and control panel PCBs (they run relatively cool), it is a great idea to replace them anyway while one is in there. That brings everything on the same 'capacitor clock' (for another 30 years countdown...;-). It is also a great idea to re-solder all the wire to board headers since they tend to develop bad solder joints over time. Here are a few impressions of my progress:

This shows the board under the control panel switches and sliders in its original condition:

And after replacing the capacitors:

On to the preamplifier board:

In original condition:

and after rebuilding it:

The FM tuner has two boards, the front end and the detector part:

This shows them after exchanging the capacitors:

On to the display and uComputer boards!

Beomaster 8000: Step Three - Replacing the Main Reservoir Caps

No power supply restoration of a Beomaster 8000 is complete without also replacing the four big cans in the back. They are the reservoir capacitors for the output amplifier ±54V power rails. One 10000 uF capacitor per polarity and channel - massive! That gives the Beomaster 8000 its excellent output stability at 150W per channel. Awesome!

Here are a few impressions of my process:

This shows the original capacitors on the right side:

I unsoldered and pulled them out and replaced them with modern 105C grade Japanese units. As usual, modern capacitors are a bit more compact than 1980s types. That is why I use 3D printed adapters to fit them into the capacitor bays of the Beomaster 8000. This picture shows the original capacitors and the modern replacements with their 3D printed adapters:

The adapters and capacitors are available as a kit, just send me a message using the contact form on the right

After the installation it turned out that I broke off one of the resistors at the thermal switch for the right side:

This happens frequently when pulling out the capacitors, since the resistors are in the way, and they cannot take much bending. I replaced both resistors with new ones:

Then it was time to turn this 8000 around and do the left side:

After replacement:

After this I measured the capacitance of the original caps and of course they were out of spec (they usually are at this point):

4000uF is less than half of the specced 10000uF, but this would still have worked at moderate volume settings. But of course, the caps would have failed in the near future. So it was the right thing to replace them now for piece of mind. 

An then it was finally time to turn this Beomaster 8000 on for the first time:

And of course, one of the segments in the input display was a no-show. No problem, since I usually rebuild these displays anyway with SMD LEDs to ensure stability in the years to come. These displays all will fail in the near future, i.e. it is almost better to buy a Beomaster with failed display for less money and then fix it. That way one has a Beomaster with displays that will likely last another 30 years.

On to recapping the rest of the unit!

Beogram 8000: Installation of a Grounding Switch, Repair of a Broken Off PCB Post and, Finally!, Test Drive with Gabor Szabo!

I gave the Beogram 8000 that I am restoring right now a couple final touches:

1) As usual, I installed a switch that makes a connection between system and signal grounds. Such a connection usually extinguishes any hum that may arise from incompatible connections between turntable and amplifier. In my view there are no adverse effects resulting from connecting the two grounds, but the original B&O set-up is to keep them separately until they meet in the amplifier, so I put in a switch to make the connection easily reversible, if desired down the road.

This shows the installed switch on the output relay board:

2) I needed to reattach a broken off PCB mounting post. The post that holds the rubber bumper that presses the main PCB into its mounting brackets broke off when I removed the PCB...this old plastic can sometimes be a bit brittle. Luckily, there was enough 'meat' that allowed me to drill a small hole through the post and the underlying plastic with my Dremel tool. Then I bolted it down with a 2-56 screw and this worked very nicely:

All good now under the hood!

I closed it up and then performed a calibration of the tracking weight:

And then it was finally time for a test drive! I had just received a new vinyl from Sweden: Gabor Szabo's "Small World" from 1972. This is one of those he recorded in Sweden. I got the original Bellaphon release (Made in West Germany...;-)

What a great record (especially after ultrasonically cleaning it with my CleanerVinyl Pro..;-)! And his awesome 1970's purple outfit! Those were the days! The album contains another version of 'people', which is one of my favorite tunes ever. And Szabo brings it to life like no other. Too sad that his life was short and things did not end that well for him. Very unfortunate! I am very grateful, though, he left us a bunch of wonderful albums to enjoy! More achievement than most of us will ever be able to claim when we go meet our Maker for that final exit interview...;-)! This is Beolove!

Beogram 8000: Re-Attaching the Aluminum Panels

Time for getting pretty! The Beogram 8000 that I am restoring right now is now running nicely. But, like in most of these units, the aluminum panels are detached. Usually, it is no big deal to glue them back on. Here are a few impressions:

The panels were originally attached with some foam based double sided tape. The foam degrades and the panels come off. This is what one typically finds:

A gooey sticky soft mess! Very difficult to remove. I usually put ethanol drenched paper towel wads on there (make sure the veneer is not touched) and then wait for 30 mins:

After that the goo has softened up and can be scraped off with a plastic razor blade. Some residue remains, but this does not matter:

Then I usually glue 4-40 washers to the enclosure as spacers. I use quick setting epoxy:

Then I add some more epoxy on the top of the washers and place the aluminum panel:

Once it is in place, I secure it with carpenter's clamps and a weight for the top right corner, which is not accessible with clamps. This step is crucial, since one essentially only has one shot with epoxy. If you try this at home, make sure that the panel is really in the right spot. Applying the clamps often shifts the panel a bit, i.e. it needs to be kept aligned during the clamping process.

The next step was to put the lid back on. Unfortunately, someone already reattached it once with Gorilla glue and the panel came off again. The glue residue proved very well attached to the plastic hinge and I was not able to remove it.

since the glue residue was flat enough and its thickness similar to 4-40 washers, the situation could be rectified by adding a good amount of epoxy to the residue and more importantly to the regions that were uncoated in between, and placing the lid on top:

Again I secured it with clamps and used a pen to press the hinge upward above the power cord opening. This did the job!

Beomaster 8000: Step Two - Rebuilding the Power Supply

In electronics you usually have three things, power supply, high current loads and small current signal circuits. The smoke typically occurs when high current loads go haywire and then overpower the supply. That is why in every Beomaster 8000 that crosses my bench I first rebuild the output amplifiers. They are the main power consumers in the 8000, and therefore have the 'means' to cause significant trouble. Once the load side is reasonably stable, it is time to make sure that the supply side is sound, too. Bad reservoir capacitors can cause short circuits, and that often leads to smoke, too. Another frequent issue with supplies is that poor reservoir caps cause significant ripple, which can cause hum or microcontroller malfunctions. So here we go: Step 2 - rebuilding the power supply:

This shows the power supply board in its original condition:

And after replacing all the electrolytic capacitors with 105C grade Japanese units:

I checked the reservoir caps, and it turned out that one was on the verge of going out of business. Its capacitance was less than 1/3 of its spec:

This means that the other caps are likely not far behind, and that replacing them is a necessary step for trouble free operation down the road. After this 'satisfying' measurement, I put the board back in:

The next step is to replace the main reservoir capacitors for the ±54V rails. And then the power end of things should be good again.

Beogram 8000: Mechanical Adjustments, Carriage Belt and Spindle Lubrication

After restoring the brake circuit, the Beogram 8000 that I am restoring right now started to work again pretty well. But before a test drive I wanted to make the necessary mechanical adjustments, install a new carriage belt and clean the carriage slide mechanism.

Here are a few impressions of my progress:

The arms were quite out of whack. Both lateral,

and vertical parallelism were off considerably:

The lateral adjustment is easily done with a screw on the left side of the carriage assembly:

The vertical adjustment unfortunately requires that the carriage is take off the rails and turned around to get to the screw that is underneath:

This was the perfect moment to give the dirty spindle

a rejuvenating clean and lube:

I also cleaned the rods and put a bit of silicone grease on their surfaces. Then I put the carriage back on and checked the vertical parallelism:

Very nice! Add a new belt:

and the unit was close to be ready for a test drive. If there just weren't those (as usual) fallen off aluminum panels!